III SALE PA—LIFE-HISTORY 107 
which are for a time masked by the phenomenal activity of 
certain cells of extraneous origin, the “kalymmocytes,” derived 
from the follicular epithelium surrounding the ovum. These 
follicular kalymmocytes migrate into the ovum, surround groups 
of blastomeres, and arrange themselves so as to reproduce the 
essential structure of the future embryo for which they form 
what may be termed a scaffolding or temporary support. After 
a time the blastomeres become active, proliferate rapidly, and 
finally press upon and absorb the kalymmocytes, and so eventu- 
ally take their proper place in building up the organs. Some 
observers regard the kalymmocytes as being passive and nutritive 
only in function. 
Fic. 67.— Young _ solitary 
Salpa democratica-mucro- 
nata attached to the 
parent by the placenta. 
atr.ap, Atrial aperture ; 
br, dorsal lamina ; cil.gr, 
dorsal tubercle; ei, 
\ I 
COTTE elaeoblast ; end, endo- 
Bz \, Vik style; n.gn, nerve-gang- 
lion ; oes, oesophagus ; 
or.ap, branchial aperture ; 
peric, pericardium ; pi, 
placenta ; rect, intestine ; 
stol, stolon ; stom, stomach. 
(From Parker and Has- 
well, after Salensky.) 
At an early period in the development a part of the surface 
of the embryo, on its ventral edge, becomes separated off, along 
with a part of the wall of the cavity (“ oviduct ”—a diverticulum 
from the atrium) in which it lies, to form the “placenta” (Fig. 
67, pl) in which the embryonic and maternal blood-streams 
circulate in close proximity, and so allow of the conveyance of 
nutriment to the developing embryo by means of large migrating 
placental cells. At a somewhat later stage a number of cells 
placed at the posterior end of the body alongside the future 
nucleus become filled up with oil-globules to form a mass of 
nutrient material—the “elaeoblast” (Fig. 67, eb/)—which is 
used up later in the development. Many suggestions have 
been made as to the homology and meaning of the elaeoblast ; 
but it may now be regarded as most probable that it is reserve 
food-material associated with the disappearing rudiment of the 
